The present invention belongs to the technical field of liquid droplet ejection apparatuses used in ink jet devices for recording or coating by ink droplets ejected from an ink droplet ejection surface onto an open space and flying therein, and, more particularly, relates to a liquid droplet ejection apparatus of a new structure that does not have individual fluid flow paths associated with individual ejection units and also to an inkjet recording head utilizing this liquid droplet ejection apparatus.
Thermal inkjet systems in which ink droplets are ejected from nozzles by the expansion force generated by rapidly vaporizing a portion of ink under heating with heaters is applied to various printers and plotters (See JP 48-9622 A, JP 54-51837 A, etc.).
Further, there is also known an electrostatic type or piezoelectric type inkjet printer or inkjet plotter in which ink droplets are ejected from nozzles by the energy generated by vibrating diaphragms by actuators making use of static electricity, a piezoelectric element or the like (See JP 11-309850, etc.).
An inkjet recording head that performs inkjet image recording generally comprises a large number of nozzles arranged in one direction, ink ejection units such as heaters or actuators provided to the individual nozzles, individual flow paths for feeding ink to the respective ejection units (nozzles) or ink chambers for the respective ejection units, and an a common ink flow path for feeding ink to the individual ink flow paths or ink chambers.
Further, to the common ink flow path, ink is fed from an ink tank mounted on a printer (head unit) via an ink feed path formed in a frame on which an inkjet recording head is mounted.
Such an inkjet recording head is manufactured by utilizing a semiconductor manufacturing technology which can perform minute processing even an inkjet recording head that has so high a nozzle density that exceeds 600 npi (nozzle/inch) is already realized.
However, in the known inkjet recording head having the structure described above, it is necessary to provide a large number of nozzles and individual ink flow paths or ink chambers for feeding ink to ejection units corresponding to the respective nozzles; this turns out to be an obstacle to a further scale-down in some cases.
It is an object of the present invention to solve the prior art problems described above by providing a liquid droplet ejection apparatus utilized in an inkjet recording head, etc. and, more particularly, a novel liquid droplet ejection apparatus which can eliminate the need for a large number of nozzles for ejecting liquid droplets, and liquid feed units which are provided independently for each liquid droplet ejection and which includes individual ink flow paths formed for the respective nozzles or ejection units such as heaters or actuators corresponding to the respective nozzles.
Another object of the present invention in to provide an inkjet recording head utilizing the above-mentioned liquid droplet ejection apparatus.
In order to attain the object described above, the first aspect of the invention is to provide a liquid droplet ejection apparatus comprising a liquid holding material which has three-dimensional voids communicating three-dimensionally with one another at least up to a liquid droplet ejection surface, and an array of a plurality of ejection devices each of which applies ejection energy to a part of liquid held in the three-dimensional voids of the liquid holding material thereby ejecting fine liquid droplets from the liquid droplet ejection surface, wherein the fine liquid droplets are ejected in accordance with each of the ejection devices of the array.
Further, in order to attain another object described above, the second aspect of the invention is to provide an inkjet recording head in which a liquid droplet ejection apparatus is used for an ink ejection means as it is or in a form of a one-dimensional, two-dimensional or three-dimensional arrangement, wherein the liquid droplet ejection apparatus comprises a liquid holding material which has three-dimensional voids communicating with one another at least up to a liquid droplet ejection surface and an array of a plurality of ejection devices each of which applies ejection energy to a part of the liquid held in the three-dimensional voids of the liquid holding material thereby ejecting fine liquid droplets from the liquid droplet ejection surface, wherein the fine liquid droplets are ejected in accordance with each of said ejection devices of the array.
Here, each of the ejection devices of the array is preferably driven individually.
Alternatively, two of more of the ejection devices of the array may be driven simultaneously by one driving source.
And, preferably, the liquid holding material is a thin porous material having the three-dimensional voids communicating three-dimensionally with one another at least up to the liquid droplet ejection surface and in directions across the material generally perpendicular to a direction toward the liquid droplet ejection surface.
Preferably, the porous material is a porous film having the three-dimensional voids communicating three-dimensionally with one another at least up to the liquid droplet ejection surface and in directions across the film which are generally perpendicular to the direction toward the liquid droplet ejection surface.
Preferably, each of the ejection devices in the array is disposed on a surface side of the porous material opposite to the liquid droplet ejection surface and is a thrusting means for thrusting a part of the liquid in the porous material in the direction toward the liquid droplet ejection surface.
Preferably, the thrusting means is an actuator which thrusts the porous material and the liquid held therein in the direction toward the liquid droplet ejection surface.
Preferably, the actuator is a bimorph type piezoelectric element.
Preferably, the porous material has elasticity and the thrusting means is disposed in a state in which the thrusting means is substantially in contact with the surface side of the porous material opposite to the liquid droplet ejection surface.
Preferably, the thrusting means uses a heater for heating the liquid to be ejected as the fine liquid droplets to generate an air bubble thereby thrusting a part of the liquid in the porous material in the direction toward the liquid droplet ejection surface.
Preferably, the ejection devices are disposed in a state in which the ejection devices are substantially in contact with a surface side of the liquid holding material opposite to the liquid droplet ejection surface.
Preferably, the fine liquid droplets have a size as defined by a size of each of the ejection devices to be driven.